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(N0 Mom. 2 sheets sheet 1. EL T. GREENPIELD.

SAFETY CIRCUIT FOR ELECTRIC LIGHTS.

N0. 355.446. y Patented Jan. 4, 1887.

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SAFETY CIRCUIT FOR ELIEGTRZEG LIGHTS. No. 355,446. Patented Jan. 4, 1887,.

UNITED STATES PATENT OFFICE.

EDWIN T. GREENFIELD, on NEW YORK, N. Y., ASSIGNOR ro HIMSELF AND sIeMUND BERGMANN, on SAME PLACE.

safety wire accompanying the electric con-.

SAFETY-CIRCUIT FOR ELECTRlC LlGHTS.

SPECIFICATION forming part of Letters Patent No. 355,446, dated January @1887.

Application tiled July 3, 1886. Serial No. 207.063. (N0 model.)

To aZZ 1072,0722, it may concern.-

Be it known that l,,EDwrN T. GnnnNFrnLD, of the city and State of New York, have invented an Improvement in Safety Devices for Electric Circuits, of which the following is a specification.

In placing the wires into buildings for electric lighting or other purposes it is usual to make use of conductors covered with an insulating and fire-proof composition; but it is well known that this fire-proof composition is not always strictly water-proof, and that by continual exposure to moisture such moisture will sometimes penetrate to the conductor.

I have discovered that a danger of fire exists from electric wires under circumstances where the conductors are exposed to moisture, because such conductors usually rest upon wood-work, and where in the building such wood-work and the conductor become moist, by the escape of steam in steam-heating apparatus or by leakage from water-pipes or otherwise, the moisture becomes a s'uflicicnt conductor to short-circuit a portion of the current, and this shunt or short circuitis often of such resistance that the partsbecome intensely hot, so as to set fire to the wood-work.

By myirnprovement Iintroduce a neutral or ductors, and I combine with these an indicating or safety device whereby the current diverted through moisture will be made use of to give an alarm or to out out the circuit where the danger exists, so that the current will cease to pass where there is moisture, and the current in that portion of the circuit will be interrupted until the repairs are made or the defect remedied.

In the drawings I have represented by a diagram, Figure Lone of the ways in which my improvement may be niadeuse of, and in Fig. 2 a cut-out coil in the shunt-circuit. Fig. 3 shows the conductors and thc'safetywire as included in one envelope. Fig. 4 represents the neutral wire as applied with working devices in series, and Fig. 5 shows two neutral wires to form a complete circuit.

The main conductors 2 and 3 are connected with the branch conductors 4 and 5, and between the latter the incandescent or other lamps or other appliances for using electriccurrents are introduced, as at 6.

My improvement may be applied separately to each branch circuit or there may be several branch circuits connected to the safety apparatus. It is preferable not to include too many branch circuits with one of the safety devices, because of the inconvenience arising from interrupting the current in all parts of the entire circuit that is connected with the apparatus and from the difficulty in locating the source of danger.

I make use of a neutral or safety wire, 7, running along with the electric conductors, and it is preferable to inclose this third wire 6 in the same winding or envelope that contains the conductors, as illustrated in Fig. 8, and I introduce a safety-catch, fusible wire, electromagnet alarm, or other suitable apparatus in a circuit to one of the conductors, which ciro cuit also includes the neutral or safety wire, in order that when the circuit between either of the electric conductors and the neutral or safety wire is closed by the presenceof moisture the currentwill pass from such conductor 7 through the safety-wire and the fusible plug, magnet, or other device, and either short-air cuit the current, give an alarm, or break the circuit to the conductors where there is moisture, so that the source of danger may be stopped.

In Fig. 1 I have represented the safety-wire 7 as leading to the helix 8 of an electromagnet, and thence by the wire 9 to the negative wire 2. There is also a branch wire, 10, to $5 the armature 11 and another wire to the front stop, 12, so that when the current may be caused to pass through the electro-magnet 8 by the presence of moisture the armature 11 will be attracted and short-circuit the current through 10, 11, 12, and 9, and thereby melt one or both of the safety-wires or other d vices, 15 .15, Fig. 1, in the electric circuit, and cut olf the current.

If there is a helix ofGerman-silver wire, 16, connected with the wire 7 and surrounding a fusible wire, 15, in the main circuit, the current shunted through the wire 7 by the presence of moisture will develop sufficient heat in the helix 16 to melt the fusible wire 15 and break the circuit.

It will also be apparent that the current passing through the helix 8 may be availed of to ring an alarm-bellsuch as at 200r to give any other indication, so that danger may be recognized and proper measures taken to prevent fire from the shunting of an electric current through moisture between the conductors, as before described.

In Fig. 4 I-have illustrated the same circuitconnections and helix as in Fig. l, but have represented the lamps or other working devices 6 as in series instead of beingin multiple arc.

In Fig. 5 I have shown two safety or neutral wires running to the helix 8 of the electromagnet. Under almost all circumstances acurrent shunted or leaking from either conductor will traverse these two wires and the helix of the electro-magnet in consequence of differences in resistance to the current through the moist ure, and the electro-inagnet is energized and will sound an alarm or give any desired indication. I have shown the armature as acting, when moved, to close a shunt-circuit between the two main conductors, and thereby cause heat to be developed in the fusible wires 15 and cut off the current to the place where there is moisture; but in all cases the current passing over the safety or neutral wire or wires may be availed of in any desired apparatus to give an indication or warning. The electromagnet in Fig. 4 may simply close a switch to short-circuit the current, so that it will not pass to the lamps beyond. This is especially available where there are other lights or working devices in the same circuit. In this case the fusible safety device 15 may be dispensed with.

I claim as my invention 1. The combination, with the covered electric conductors in an electric circuit, of an adjacent neutral or safety wire or wires and an indicating apparatus, and a connection between the same and one of the electric conductors, whereby the presence of a false current or leakage due to moisture will be indicated, substantially as set forth. 7

2. The combination, with the covered electric conductors in an electric circuit, of an adjacent neutral or safety wire connected at one end with one of the conductors, and a fusible wire acted upon by the current shunted by moisture from the conductors, substantially as set forth.

3. The combination, with the covered electric conductorsin an electric circuit, of an adjacent neutral or safety wire and a circuit including the helix of an electro-magnet, whereby such electr c-magnet will be energized to give an alarm or otherwise when a current is shunted over the safety-wire through moisture between such safety-wire and one of the con ductors, substantially as set forth.

4. The combination, with the conductors in an electric circuit, of an adjacent neutral or safety wire and an indicating or alarm apparatus connected therewith to be brought into action by a current shunted from either main conductor, substantially as set forth.

Signed by me this 28th day of June, A. D. 1886.

E. T. GREENFIELD.

Witnesses:

GEO. T. PINCKNEY, WILLIAM G. Moira. 

